Abstract
A fast, simple, sensitive cathodic adsorptive stripping voltammetric procedure for quantitative analysis of Cd–oxine complex in al-Madinah city water samples and human plasma is described. The technique involves adsorptive accumulation of the complex on the working electrode, followed by square wave voltammetric determination of the preconcentrated analyte. In basic media, a cathodic electrochemical process involving the elimination of two protons occurs, and a mechanism for the reduction process is suggested. The optimal experimental parameters for assay of this complex are: carbonate supporting electrolyte pH 8, accumulation time 30s, accumulation potential −0.1V, scan rate 200mVs−1, pulse amplitude 80mV, frequency 40Hz, surface area of working electrode 0.6mm2 and convection rate 1000rpm. The calibration graph for determination of Cd–oxine was linear over the concentration range 5×10−8 to 4×10−7moll−1 (r=0.998), with a detection limit of 3.5×10−9moll−1. The precision of the proposed procedure was estimated by 10 successive voltammetric measurements of 2×10−6moll−1 Cd with 4×10−6moll−1 oxine, and the calculated relative standard deviation was 0.39%. The percentage recovery, indicating the accuracy of the analytical method, was 94±1.0%. Possible interference by several substances, including metals and ligands, was also evaluated. The electroanalytical method was successfully applied to assaying cadmium in water samples and biological fluids such as plasma.